Peroxidase activity and polyamine changes in response to ozone and simulated acid rain in Aleppo pine needles

Three-year-old plants of Pinus halepensis Mill. were exposed to ozone (100 ppb) and simulated acid rain (pH 3.4) separately or combined, over a 2-month period while grown for 2 years in climate-controlled growth chambers. Current year and 1-year old needles were sampled for biochemical analysis. Peroxidase (POD) activity showed a positive response to combined treatment in current year needles (c-y needles) but a markedly reduction of POD was observed in 1 year needles (1-y needles) from the same treatment. An experiment with ozone or acid rain demonstrated that the change of POD activity is mainly due to ozone. Polyamines putrescine and spermidine increased in younger tissues (c-y needles) with a combined treatment; a less clear effect was found in older needles although polyamine content was always higher in heated than in control plants. The possible role of polyamines and peroxidases in response to ozone and simulated acid precipitation is discussed.